Step #1 mix the kidney beans, onion, & pickle relish in a large bowl, mixing well, celery, then set aside.
Step #2 mix the vinegar, then cook over low heat/flame, mixing well, stirring constantly, egg & mustard in 1-quart saucepan, sugar, 7 mins or until the mixture thickens.
Step #3 remove this from the heat.
Step #4 Pour the vinegar mixture over the vegetables, tossing carefully to coat well.
Step #5 Cover & put in the fridge at least 6 hrs before serving.